Fixed #25068 -- Added metaclassmaker to resolve metaclass conflicts in migrations state.

[kosz85]

#4968

Now it's faster, or more like it's not slowing down ;)

[timgraham]

@MarkusH - could you run your benchmarks on this or share how we can do it? I'll happily review the patch for style, etc. if it passes that stage of review.

[MarkusH]

I just use https://github.com/MarkusH/django-migrations-benchmark as some kind of benchmarking tool and uncomment the code in Django I don't want to have affect on the timing.

[kosz85]

@MarkusH I used your benchmark, it seems my current solution doesn't slow down migrations. I have two thoughts after using your benchmark :) Please add __init__.py to your benchmark apps :) It will be easier to use by everyone that need to test it. And second one: this doesn't test my case, so after merging it would be nice to improve it and test also models with multiple metadatas.

Here are results, I ran it when working as I don't have spare computer so it's not best measurement, but I think is enough. As you can see it's almost the same, even better with fix, but difference is caused by IO.

With fix
real    7m7.687s
user    3m4.366s
sys 0m3.366s

real    7m15.488s
user    3m4.684s
sys 0m3.174s

Without fix
real    7m36.196s
user    3m16.878s
sys 0m3.293s

real    7m24.973s
user    3m11.605s
sys 0m3.414s

[MarkusH]

Mixin should come before models.Model

[kosz85]

I will change it, but you know that this doesn't really matter here? ;) It's just for you.

[MarkusH]

Can you make ItermidiateMetaClass and DummyMetaClass each add an attribute the object, please.

[kosz85]

IntermediateMetaClass shouldn't add additional attrs as this is only "merging" object, as Python is not doing it automatically.
I added attr to DummyMetaClass as suggested.

[MarkusH]

You don't need this pass anymore.

[kosz85]

hehe, you are right :) You want to tire me with this topic to death ;) will fix in minutes.

[MarkusH]

@timgraham if you want to merge, patch looks good to me.

[MarkusH]

Closed in favor of #5334